It depends on what you like/want from a lens...
I want the sharpest image with the least distortion, and for the prices they're charging I want these qualities across the entire frame. These Z SLR lenses seem to be highly center-optimized, some more than others. I don't want to make it sound like they suck. Not at all. Just that only one or two of them offer a meaningful image quality improvement over the equivalent focal lengths available from Canon/Nikon, and they are expensive. What I will say though is on the subject of flare/ghosting, Zeiss always excels. T* is still the best coating out there in my opinion. The other thing I'll agree on is the mechanics and build quality are excellent. They are a joy to hold and use.
But if people want them I'm happy to part with my 25mm and 50mm, barely used, mint condition ZFs.
Aren't those new Zeiss SLR lenses actually made by Cosina?
Yes they are made by Cosina. I don't consider that a problem though. They just don't seem to be designed in a way that makes them significantly better, or any better than the Canon and Nikkor equivalents.
My experience of Zeiss lenses is mostly with an older generation, in Rolleiflex mount.
I certainly woudn't describe any of the ones I've had or used as "highly center-optimized".
I've also extensively used Nikkor primes of the AI/AIS generation (many of the better ones too) and can compare them directly to the Zeiss ones: In my experience the Zeiss lenses *are* often significantly (as in somehow visibly) better even using the usual parameters (sharpness across the field, distortion & vignetting). Exceptions being perhaps the 105 2.5 & the 180 ED.
That said, again IMHO, where the better Zeiss lenses shine (pun intended) is in their flare control, colour rendition and 3-d effect. In short, their general "look".
That may sound a bit esoteric, but simply is...
Just a question: it seems that many who are dissatisfied with the new Zeiss lenses aren't using them with film (which adds a whole can or worms of various interactions and so on), is that your case?
I don't think they can really be compared to the medium format Zeiss offerings for Hasselblad or Rollei. As I said earlier I agree flare control always seems a step above the rest when it comes to anything with T* coatings.
I'm a 100% film user. Don't own any digital equipment. My gut feeling with these lenses was always that Zeiss assumed many people would use them with digital, and that many of those people would be using digital cameras with smaller sensors than full frame, meaning they'd have a sweet spot advantage since they aren't using the edges of the image circle. Zeiss also paid alot of attention to bokeh, which is useless to me, although others might value these qualities for shallow depth of field photography etc.
So Zeiss kind of slacked off on the edges and corners with some of these, in particular the 25mm, which I was most disappointed with. It has a significant amount of barrel distortion too. I was never thrilled with the 24mm Nikkor offerings so I was initially really excited when the 25mm ZF came out. Big let down. Why don't any of these expensive Zeiss lenses have precision ground aspherics for example?
The 50mm 1.4 planar? Forget it. My lowly Nikkor AF 1.4D is every bit as sharp and contrasty, just as well corrected, and has slightly less distortion. The Planar probably has the edge on flare control in backlit situations etc, but to me a 50mm lens that expensive should, for example, have imperceptible distortion.
The 35mm f2 is quite good, and sharper around the edges than my 35mm f2 AF-D Nikkor, but the Zeiss has noticeably more distortion.
The 21mm is also quite good. It looks very sharp to me all the way to the corners though it still has too much mustache-style complex distortion for a lens that price (there are some newer wide angle Nikkor zooms that have negligeable distortion at focal lengths like 21mm and 24mm).
Those are the 4 I own. I didn't bother with the 85mm because the two Nikkors I have in that focal length are razor sharp and distortionless. Some have suggested the 50mm f2 makro is an excellent lens, but it's way too expensive for me to consider.
I just don't think they are all they appear to be when you look at them and feel how solid they are. Just not worth the money from an optical perspective in my opinion.
The Zeiss lenses I was talking about are for Rolleiflex 35mm SLRs (several models built between c. 1970 and the 1990's). Often, but not always optically the same as the Yashica/Contax lenses...
Some of the new lenses are definitely different (a 35mm f/2.0 didn't exist and the 18mm has a different nominal aperture) and it seems to be debated whether others are exactly the same as their old versions.
That said, apart from the 15mm & 18mm, I have very different results regarding edge sharpness and distortion (15mm - Leica version, 18mm, 25mm, 35mm 1.4 & 2.8, 50mm 1.4 & 1.8, 85mm 1.4 & 2.8, 200mm).
The lack of aspheric elements seems to be part of Zeiss' design philosophy.
While Leica, for example, embraced aspherics and I admit that later Leica lenses are technically better than my Zeiss', I still like the overall "look" of the Zeiss' better.
The degree to which distortion is visible and bothersome depends on the type of photography, so it may be in the work you're doing you simply don't notice it, or it is not detrimental. For the stuff I do, it can be a real pain, and these Zeiss lenses, for the most part, are no better corrected for geometric distortion than their Nikon/Canon counterparts. It annoys me, but I think this might also be part of the digital crossover intent. Simple geometric distortion can be corrected with software so my sense is in general the latest wide angle and normal focal length lens designs from Nikon, Zeiss etc attempt to optimize for other things like speed and bokeh rather than distortion. For example even Nikon's new, VERY expensive 24mm prime shows visible barrel distortion.
Anyhow I guess everyone had their preference and taste. Interesting discussion.
I often photograph architecture, landscapes and artwork, in the past I was photgraphing archaeological digs and using those photos to help produce maps. So distortion *is* something I find very important (I usually hate most zooms mainly for that reason).
While I haven't done any more "pseudo-photogrammetry" since I started using the Zeiss' (the Micro-Nikkor 55 2.8 was my favorite for that), for my uses, their distortion isn't noticeable (FLs above 18mm - from 25mm on: I have no 21mm).
For example, I use my Zeiss 25mm for achitecture without a thought, while my Nikkor 24mm was practically unusable. The Nikkor 35 2.0 also fared pretty poorly.
The digital crossover intent & poor distortion correction in the newer Zeiss' could be... It'd be interesting to see some reliable measurements (Zeiss does publish thiers, though how reliable they are & how to get other manufacturers' for comparison is the question).